Fixing `.panel-details` overflowing when AJAX loader image is shown

See this screenshot: http://imgur.com/V3NAQet

This fix should work on all current major browsers, except Safari (that still requires a prefix). http://caniuse.com/#feat=flexbox
Merge pull request #5 from denilsonsa/panel-details-fix

Fix `.panel-details` overflowing when AJAX loader image is shown